Cripto is a gene recently identified and cloned from a human embryonal carcinoma cell line. The human cripto cDNA is 2020 base pairs long with an open reading frame of 564 base pairs. The open reading frame encodes for a protein of 188 amino acids that contains a control portion of 37 amino acids which shares a structural cysteine rich motif in common with other members of the EGF super gene family, such as human EGF, human TGF a and human amphiregulin. It has been demonstrated previously that the over expression of EGF or TGF a cDNAs in fibroblasts and epithelial cells can lead to transformation in vitro and in certain cases to tumorigenicity in vivo. Preliminary experiments have shown that transfection of human cripto cDNA expression vector in which transcription is under the control of RSV- LTR into mouse NIH-3T3 fibroblasts induces the formation of transformed foci. Since cripto and TGFa are expressed in undifferentiated human embryonal carcinoma cell line in which they may function as autocrine growth factors, and since a portion of the 'cripto' protein shares the homology to EGF & TGFa, we have decided to make antisense oligos against the CRIPTO cDNA sequence, in order to show the ability to shut off the function of this factor. As a preliminary step in this project, we are screening 3 different phosphorothioate oligos in antisense, sense and nonsense nature of the target sequences of the CRIPTO gene. We studied the effect on three colon carcinoma cell lines [viz NTERA-2, NOG-8, and GEO. which have been analyzed for the cripto gene] for their inhibition in cell growth. Preliminary results showed a 90% inhibition of NOG-8 colon cancer celline in soft agar growth.